Auto merge of #123337 - workingjubilee:debug-compiler-profile-expectations, r=fmease

Include line tables in compiler profile

This profile has only undergone minimal tweaks since it was originally drafted. I asked a number of compiler contributors and they said they set rust.debug explicitly. This was even true for one contributor that set `rust.debug = false`! Almost everyone seems slightly surprised that `rust.debug = true` is not the default.

However, adding full debuginfo at this level costs multiple gigabytes! We can still get much better profiling and such by setting `rust.debuginfo-level = "line-tables-only"` at the cost of only 150~200 MB on the weight of a fresh build dir from `./x.py check`.

src/bootstrap/defaults/config.compiler.toml

@@ -8,6 +8,8 @@ compiler-docs = true
 # where adding `debug!()` appears to do nothing.
 # However, it makes running the compiler slightly slower.
 debug-logging = true
+# Get actually-useful information from backtraces, profiling, etc. with minimal added bytes
+debuginfo-level = "line-tables-only"
 # This greatly increases the speed of rebuilds, especially when there are only minor changes. However, it makes the initial build slightly slower.
 incremental = true
 # Print backtrace on internal compiler errors during bootstrap

src/bootstrap/src/utils/change_tracker.rs

@@ -180,4 +180,9 @@ pub fn human_readable_changes(changes: &[ChangeInfo]) -> String {
         severity: ChangeSeverity::Info,
         summary: "New option `build.lldb` that will override the default lldb binary path used in debuginfo tests",
     },
+    ChangeInfo {
+        change_id: 123337,
+        severity: ChangeSeverity::Info,
+        summary: r#"The compiler profile now defaults to rust.debuginfo-level = "line-tables-only""#,
+    },
 ];